The present invention relates generally collapsible frame structures, and more particularly to collapsible frame structures comprising a plurality of separable frame members held together by an internal cord or cable.
Collapsible frame structures comprising a plurality of frame members that are joined end-to-end and held together by a flexible cord or cable are known. For example, U.S. Pat. Nos. 6,557,572; 4,827,958; 4,706,696 disclose tent poles comprising pole sections held together by an elastic cord. The individual pole sections can be separated and folded over to form a compact bundle for storage. The elastic cord pulls the individual frame members together to facilitate assembly. Similar frame systems may be found in other types of devices as shown by U.S. Pat. No. 6,038,802 (portable displays); U.S. Pat No. 4,215,877 (folding utility carts); and U.S. Pat No. 6,062,648 (folding chairs). Frame structures that rely on an elastic cord to hold the individual sections together are easily assembled but limited in the loads that can be supported.
It is also known to use an inelastic cable, such as a steel cable, to tension a multi-part frame structure as shown in U.S. Pat. Nos. 5,930,971 and 4,167,354. In these patents, a tension cable runs interiorly through individual frame members joined end-to-end and is tightened by means of a tensioning device after the frame is assembled to strengthen the frame. Frames that use an inelastic tension cable can support greater loads, but are not as easily assembled. Further, the tensioning devices tend to be cumbersome to operate.
Accordingly, there is a need for a collapsible frame structure that can support relatively heavy loads, and yet remain easy to assemble.